An X-ray CT system includes: a bed where to lay down a subject; a gantry configured to perform X-ray scanning on the subject lying down on the bed by irradiating the subject with X-rays; and an operation unit configured to be operated for movement of the bed, X-ray scanning, and so on.
The gantry has: a main frame; and a rotator rotatably supported by the main frame with a bearing. The rotator has: a cylindrical part; a side plate part provided at one end side of the cylindrical part; and rotator units, such as an X-ray tube, an X-ray detector, and a generator, arranged on an inner circumferential side of the cylindrical part. The side plate part has an opening formed at a central portion thereof, the opening allowing the subject lying down on the bed to enter and exit therethrough.
When the rotator is rotated, a high centrifugal force acts on heavy rotator units such as the X-ray tube and the generator. For this reason, the rotator units are arranged on the inner circumferential side of the cylindrical part, so that the cylindrical part receives the centrifugal force acting on the rotator units, and thereby prevents the rotator units from flying off due to the centrifugal force during the rotation of the rotator.
However, such a gantry for CT system as described above does not take the following points into consideration.
First, since the rotator is provided with the cylindrical part formed over the entire outer circumference of the rotator, the rotator is heavy. Additionally, since the production cost of the rotator increases substantially proportional to the weight of the rotator, such a heavy rotator requires high production cost.
Moreover, for the heavy rotator, the bearing configured to rotatably support the rotator and a DD motor (direct drive motor) configured to rotate the rotator need to be large in size. Accordingly, the cost of the gantry is increased.
Further, the rotator is made of a casted metal in many cases. Such a rotator made of a casted metal is in a shape having a cylindrical part and a side plate part. Accordingly, the rotator has to be processed in various directions in finishing processing. This increases the cost of finishing processing.